Refining process and apparatus

ABSTRACT

A process and an apparatus for refining a product placed in a trough member and in which at least one molten zone created in the product is displaced through the trough and in which the molten zones are obtained by means of induction heating through one or plural successive coils fed by in phase currents oriented in such a way that the magnetic fields between two successive coils are opposite to each other. The process is characterized in that the trough is supported on one or plural metallic rails which are water-cooled and tensioned in the longitudinal direction by elastic means, in that the induction coils are placed around the trough and the rails and are displaced along the axis of the trough, and in that the coils are connected to an alternating current generator of intermediate frequency. The apparatus comprises a support for supporting the trough containing the product to be refined and the heating equipment, small rails secured to such support and supporting the trough, elastic means mounted on the support for tensioning the rails in the longitudinal direction, a guide secured to the support and supporting a mobile carriage, an inductor comprising at least one induction coil secured to the carriage and surrounding the trough, and an alternating current generator of intermediate frequency connected to the coil of the inductor.

United States Patent [1 1 Jaequerie et a1.

1 1 Oct. 2, 1973 1 REFINING PROCESS AND APPARATUS [73] Assignee: Elphiac,Charleroi, Belgium 22 Filed: Jan. 13, 1971 21 Appl. No.: 106,027

[30] Foreign Application Priority Data Jan. 14, 1970 Belgium 83841 July 8, 1970 Belgium 91345 [52] US. Cl 75/65 ZM, 13/1, 219/1043 [51] Int. Cl C22b 9/00, H05b 7/10, H05b 5/00 [58] Field of Search 75/10, 65 ZM; 148/1.6,171,172;13/D1G.l;219/10.43

[56] References Cited UNITED STATES PATENTS 3,163,523 12/1964 Porter .1 75/10 R 3,144,357 8/1964 Hulme 75/65 ZM 3,462,321 8/1969 Vitkus 148/172 2,977,258 3/1961 Dunkle 148/172 3,124,633 3/1964 Van Run.... 148/].6 2,902,350 9/1959 Jenny 148/].6 2,985,519 5/1961 Kelemen 148/16 3,047,380 7/1962 Bloem 75/65 ZM Primary Examiner-L. Dewayne Rutledge Assistant Examiner-Peter D. Rosenberg Att0rneyRaym0nd A. Robic [57] ABSTRACT A process and an apparatus for refining a product placed in a trough member and in which at least one molten zone created in the product is displaced through the trough and in which the molten zones are obtained by means of induction heating through one or plural successive coils fed by in phase currents oriented in such a way that the magnetic fields between two successive coils are opposite to each other. The process is characterized in that the trough is supported on one or plural metallic rails which are water-cooled and tensioned in the longitudinal direction by elastic means, in that the induction coils are placed around the trough and the rails and are displaced along the axis of the trough, and in that the coils are connected to an alternating current generator of intermediate frequency. The apparatus comprises a support for supporting the trough containing the product to be refined and the heating equipment, small rails secured to such support and supporting the trough, elastic means mounted on the support for tensioning the rails in the longitudinal direction, a guide secured to the support and supporting a mobile carriage, an inductor comprising at least one induction coil secured to the carriage and surrounding the trough, and an alternating current generator of intermediate frequency connected to the coil of the inductor.

8 Claims, 3 Drawing Figures PATENTEDUBF 2 7 J2me WU NF 2 INVENTORS Jean-Marie JACQUERIE Georges, Jean-Pierre Hubert DEFOSSE Pierre-Poul LAMS REFINING PROCESS AND APPARATUS This invention relates to a refining process and to an apparatus for carrying out the process.

A process is-already known for refining a product placed in a suitable trough and in which a molten zone created in such product is displaced through the product, and in which such molten zone is obtained by means of induction heating. Such known process may be repeated several times but it is also known to displace through the product to be refined, at a small distance one behind the other, plural molten zones separated by solidified zones. To obtain such result, plural successive induction coils are fed by in phase currents oriented in such a manner that the magnetic fields between two successive coils oppose each other. In such a known process, the induction coils are fed by high frequency currents and the quantity of product refined is relatively small.

The object of the present invention is to provide a similar process, but adapted to the treatment of larger masses of material. The product in accordance with the invention is characterized by the steps of supporting the trough on one or plural small metallic rails which are water-cooled and tensioned in the longitudinal direction, placing at least one induction coil around the trough and around the rails which and displacing the coil along the axis of the trough, and connecting such coil to an alternating current generator of intermediate frequency.

The trough and the rails may be surrounded by a refractoryhousing inside of which vacuum or a suitable atmosphere may be maintained. 7

If plural induction coils are used and fed by in phase currents oriented in such a manner that the magnetic fields between two successive coils oppose each other, the heating power at the location of each induction coil may becontrolled as a function of the desired width of the molten zone.

A short-circuited winding may be placed between two successive induction coils and moved into the neighbourhood of the trailing induction coil when the combination including two induction coils is moved so as to lower the magnetic field in thetrailing induction coil because such trailing induction coil requires less power than the leading induction coil. Indeed, the leading induction coil absorbs the cold ingot whereas the trailing one which is fed by the same current asthe leading coil works on an already hot ingot and thus requires less power.

The object of the invention is also a device suitable for carrying out the above process. Such device comprises a support for maintaining the trough containing the product to be refined and the heating equipment, small rails secured to such support and supporting the trough, elastic means mounted on the support for tensioning the rails in the longitudinal direction, a guide secured to such support and supporting a mobile earriage, an inductor including'at least .one induction coil secured to such carriage and surrounding the rails and trough, and an alternating current generator of intermediate frequency connected to the induction coil of the inductor.

The invention will now be disclosed with reference to a particular embodiment of the invention and to the accompanying drawings in which:

FIG. 1 illustrates a plan view of the device in accordance with the invention;

FIG. 2 illustrates an elevation view, partly in section, of the ends of a support for the trough; and

FIG. 3 illustrates a partial elevation view perpendicular to that of FIG. 2.

The product to be refined, for example an aluminum mass 1, of plural tens of kilograms, is placed in a trough 2, for example in graphite. The trough 2 is placed on two supporting rails 3 made of stainless steel, which are water-cooled and surrounded by a refractory housing consisting of a protecting tube 4, for example in quartz. In the quartz tube 4 circulate, for example, a protecting gas such as argon. Parallel to mass 1 and to protecting tube 4 is placed a carriage 5 which may be displaced along a guide made of two bars 6. The carriage 5 supports the condensors (not shown) of an oscillating circuit, an inductor made of the two coils 7 and 8 and a short-circuited winding 9 with a device 10 for regulating the position of the short-circuited winding 9 with respect to the two coils 7 and 8. The windings 7 and 8 and the short-circuited winding 9 are connected to a water cooling system by means of flexible connections not shown. An advancing device, illustrated by a leading screw 11, permits to displace the carriage 5 with respect to the trough 2. The regulating device 10 consists of a hand wheel and a leading screw. It is obvious that such a device may be controlled by a servo-motor according to a given program or in function ofindications furnished by a measuring apparatus, not shown.

The two coils 7 and 8 of the inductor do not only surround the trough but also the rails 3 and the protecting tube 4. The coils are fed by the same current provided by an intermediate frequency generator, not shown, and oriented in such a way that the magnetic fields between the two windings oppose each other. The range :of the intermediate frequencies normally extends from 150 to 10,000 hz but may substantially exceed such range. There is so obtained molten zones which are very narrow and very well defined. For this reason, the distance between the two coils 7 and 8, selected in function of the product to be refined, may be relatively small, that is, for example, about four times the diameter of the mass 1, if such mass is aluminum.

The heating power of the two coils 7 and 8 may be different one with respect to the other. In the case where the carriage 5 is displaced slowly towards the left, the coil 7 absorbs the cold ingot and requires a power much larger than the coil 8 which follows it. Since the two coils 7 and 8 are fed by the same current, the magnetic field of the coil 8 is lowered by a shortcircuited winding 9 placed between the two coils 7 and 8 and close to winding 8. The idea of placing the shortcircuited coil 9 between the two coils 7 and 8 permits, in the case of a reversal of the direction of movement of the carriage 5, wherein the coil 8 absorbs the cold ingot, to transfer the short circuited coil 9 adjacent to winding 7 which under such a circumstance requires less power. The current flowing through coils 7 and 8 may be regulated by known regulators, not illustrated, controlling, for example, the intermediate frequency alternating current generator.

controlled by a programmed device or by one or plural measuring apparatus not illustrated The frequency of the heating current is chosen in function of the depth of desired heating; such frequency also depends on the nature of the material to be refined. In choosing the frequency, one must take into consideration, in addition, the fact that the increase of the intensity of the current which is produced for the lower frequencies may cause stirring of the molten zones. This stirring may be desirable to a certain extent, but becomes undesirable if it is too severe.

It is not essential that the number of coils be limited to two, but this is often advantageous. If the number of coils is more than two, it is sufficient to make sure that in the interval between two successive coils, the magnetic fields oppose each other and that the currents in the coils are in phase. When the coils are fed by the same current, this last condition is automatically obtained, but it is not the only way to obtain such result.

The refractory housing or quartz tube 4 is not required when the product to be refined is, for example, a noble metal, and when the trough is inert with respect to the ambient atmosphere.

The trough 2 made of graphite is relatively fragile and is placed on two rails 3. To reduce the crosssection of such rails to a minimum value, while ensuring a suitable mechanical strength thereof, and to ensure a large maneuvering facility, the rails 3 are maintained in a support illustrated in FIG. 2. The support consists of a base 12 which also supports the guide consisting of bars 6 and of the leading screw 11, not shown in FIG. 2. On the base 12 there is located a fast headstock 13 and a movable headstock 14. The fast headstock 13 is equipped with a closed supporting collar 15 for supporting the rails 3 and the refractory housing consisting of the quartz tube 4. The movable headstock 14 is equipped with a supporting collar 16 which may be opened and in which a ring or a segment of a ring 17 for fixing the rails 3 is located and the opening of which may be closed by a door 18. The rails 3 are welded on the interior surface of the segment of the ring 17 and at the other end are maintained in the closed collar 15 by means of a screw 19 arranged to maintain the rails 3 under tension through an elastic element 20. The elastic element permits on the one hand to compensate for the thermal elongation of the rails 3 during heating thereof and, on the other hand, to maintain a tension of a predetermined value on the rails.

The ring segment 17 which is retained by collar 16 and the screws 19 and the elastic elements 20 form together a tensioning device for the rails which permit to limit their sag under the weight of the trough, when full, even though the cross-section of the rails is small. Toroidal joints 23 are provided for ensuring the tightness of the refractory housing having a controlled atmosphere at the location of the passage of the rails through the collar 15.

As illustrated in FIG. 3, the trough 2 is provided with grooves 21 in which are engaged the rails 3. In this manner, the trough when loaded may be introduced or withdrawn from the door 18, guided by the grooves 21 on the rails 3 and the protecting tube 4. The protecting tube 4 is maintained by peripheral joints 22 (FIG. 2) in the closed collar 15 at one end and in the supporting collar 16 at the other end. These peripheral joints permit to ensure the tightness of the housing in spite of the elongation of tube 4 during heating.

We claim:

1. Process for the refining of a product placed in a trough in which at least one molten zone created in the product is displaced through such product and in which said molten zone is obtained through induction heating by means of one or plural successive induction coils fed by in phase currents oriented in such a manner that the magnetic fields between two successive induction coils oppose each other, such process comprising the steps of:

a. supporting the trough on one or plural small metallic rails which are water-cooled and tensioned by elastic means in the longitudinal direction;

b. placing around the trough and the rails at least one of said induction coils and displacing said coil along the axis of the trough; and

c. connecting said coil to an intermediate frequency alternating current generator.

2. Process as defined in claim I, further comprising the step of surrounding the rails and the trough by a refractory housing inside of which is maintained a protecting atmosphere.

3. Process as defined in claim 1, further comprising the step of regulating the power at the location of each induction winding by means of a short-circuited winding placed at a suitable distance adjacent to said induction winding.

4. A device for refining a product placed in a trough in which at least one molten zone created in the product is displaced through said product and in which said molten zone is obtained through induction heating, comprising:

a. a support for supporting the trough containing the product to be refined;

b. small rails secured to said support and supporting said trough;

c. elastic means mounted on said support for tensioning said rails in the longitudinal direction;

d. a guide secured to said support in parallel relationship to said trough and supporting a mobile carriage;

e. an inductor comprising at least one induction coil secured to said mobile carriage and surrounding the rails and the trough; and

f. an alternating current generator of intermediate frequency connected to said induction coil of said inductor.

5. A device as defined in claim 4, further comprising a refractory housing surrounding the rails and the trough and surrounded by said inductor.

6. A elastic means as defined in claim 4, wherein said device for tensioning the rails comprise a first headstock having a supporting collar including means for securing one end of the rails, and a second headstock having another supporting collar including means for elastically supporting the other end of the rails.

7. A device as defined in claim 4, wherein the inductor is composed of at least two induction coils connected in series to an intermediate frequency altemat ing current generator, and further comprising a shortcircuited winding placed between said two induction coils and a device for regulating the position of said short-circuited winding with respect to said two windings.

8. Process for the refining of a product placed in a trough in which at least one molten zone created in the product is displaced through such product and in which c. placing a short circuited winding displaceably between two successive induction coils, and moving said short circuited winding into the neighbourhood of the trailing induction coil with respect to the movement of the coils of said at least two induction coils for lowering the magnetic field in said trailing coil; and

d. connecting said induction coils to one or plural intermediate frequency alternating current genera tOl'S. 

2. Process as defined in claim 1, further comprising the step of surrounding the rails and the trough by a refractory housing inside of which is maintained a protecting atmosphere.
 3. Process as defined in claim 1, further comprising the step of regulating the power at the location of each induction winding by means of a short-circuited winding placed at a suitable distance adjacent to said induction winding.
 4. A device for refining a product placed in a trough in which at least one molten zone created in the product is displaced through said product and in which said molten zone is obtained through induction heating, comprising: a. a support for supporting the trough containing the product to be refined; b. small rails secured to said support and supporting said trough; c. elastic means mounted on said support for tensioning said rails in the longitudinal direction; d. a guide secured to said support in parallel relationship to said trough and supporting a mobile carriage; e. an inductor comprising at least one induction coil secured to said mobile carriage and surrounding the rails and the trough; and f. an alternating current generator of intermediate frequency connected to said induction coil of said inductor.
 5. A device as defined in claim 4, further comprising a refractory housing surrounding the rails and the trough and surrounded by said inductor.
 6. A elastic means as defined in claim 4, wherein said device for tensioning the rails comprise a first headstock having a supporting collar including means for securing one end of the rails, and a second headstock having another supporting collar including means for elastically supporting the other end of the rails.
 7. A device as defined in claim 4, wherein the inductor is composed of at least two induction coils connected in series to an intermediate frequency alternating current generator, and further comprising a short-circuited winding placed between said two induction coils and a device for regulating the position of said short-circuited winding with respect to said two windings.
 8. Process for the refining of a product placed in a trough in which at least one molten zone created in the product is displaced through such product and in which said molten zone is obtained through induction heating by means of two or more successive induction coils fed by in phase currents oriented in such a manner that the magnetic fields between two successive coils oppose each other, such process comprising the steps of: a. supporting the trough on one or plural small metallic rails which are water-cooled and tensioned by elastIc means in the longitudinal direction; b. placing around the trough and the rails at least two of said induction coils and displacing them as a whole along the axis of the trough; c. placing a short circuited winding displaceably between two successive induction coils, and moving said short circuited winding into the neighbourhood of the trailing induction coil with respect to the movement of the coils of said at least two induction coils for lowering the magnetic field in said trailing coil; and d. connecting said induction coils to one or plural intermediate frequency alternating current generators. 